138 



THE ELASMOBEANCH FISHES 



and on the dorsal side, but unlike that of Heptanchus it passes backward 

 within the intestinal wall, making a half-loop before it empties into the ventral 

 side of the duodenum. In its course it becomes thrown into a series of ridges 

 much like the ridges in the seminal vesicles of some Elasmobranchs. 



PANCEEAS 



The pancreas (fig. 137) in the adult consists of two lobes. One of them, the 

 dorsal lobe (pw.^) , runs parallel with and over the terminal part of the cardiac 

 stomach and near its middle part sends a bridge over the pylorus to join the 

 ventral lobe (pn.'^) which is closely bound to the ventral surface of the proxi- 



..pn; 



A B 



Fig. 137. The pancreas and associated structures. A. Acanthias, dorsal view. (From Kan- 

 torowicz.) B. Squalus sucMii, dorsal view. (Chester Stock, orig.) 



d.ch., bile duct or ductus choledochus from the liver; ia., intraintestinal artery; iv., intra- 

 intestinal vein; pn.^, dorsal lobe of pancreas; pn.^, ventral lobe of pancreas; p.d., pan- 

 creatic duct ; sph, spleen. 



mal part of the middle intestine. In all specimens which I have examined the 

 pancreatic duct (p.d., tig. 137b) empties into the duodenum much as was de- 

 scribed ior Heptanchus (p. 124). 



SPLEEN 



The spleen, although not connected by ducts leading to the digestive tract, 

 is located in the mesentery and may be regarded as an organ made up of cells 

 specialized from the connective tissue of the mesentery. In sharks it is often 

 triangular in shape and its characteristic position (spl., fig. 137a) is on the 

 greater curvature of the stomach, that is, on the outer angle between the 

 cardiac and pyloric divisions. In the rays (see p. 187, fig. 175, spl.) it is a lobu- 

 lar or round structure located in the angle of the lesser curvature of the 

 stomach. In Heptanchus we have observed that the spleen takes a generalized 

 form in which it extends along the outer angle of the stomach and across the 



